I've been looking at the various postings over the past few days on how
the Kastonome works.  I think there's a simpler way of describing it.

The Kastonome system contains a restriction pouch which when inflated
blocks the air flow between the note pneumatic and the suction supply.
The flow of air from the note is therefore forced through a restriction
(a small opening).  The pneumatic is evacuated slowly, so the note
plays softly.

When the Kastonome accent hole for a particular note is open, the
restriction pouch collapses and so the flow of air from the pneumatic
is unrestricted.  The pneumatic is evacuated faster, and the note plays
louder as a result.

Because there is a tracker bar opening for each restriction pouch, this
is a true single-note accenting system.  The suction supply is the same
to all notes.  Accenting one note has no effect on any other note.

The practical implementation is more complex, but the above describes
the concept.  As constructed, the restriction pouch inflates only when
the note plays, using air from the tracker bar.  When a Kastonome
accent hole is uncovered, it blocks the passage between tracker bar and
restriction pouch, so the pouch does not inflate when the note plays.

The restriction device is inserted immediately behind the secondary
valve, blocking the flow of air from the pneumatic to the suction
supply, but not blocking the flow of air back into the pneumatic when
the note stops playing.  Because of the way the restriction device
is designed, it is simply added into the ordinary Autopiano stack,
I understand.

The drawback of the system is fairly obvious: the soft playing is based
on a simple restriction in the flow path.  All other systems set the
soft playing level against a spring using some form of regulator which
may be adjusted.  The Kastonome relies totally on the operation of each
restriction pouch.  If the pouch fails to block the unrestricted path
fully, some air leaks past and notes play louder even when not
accented.  The level of the soft playing cannot be regulated without
individually adjusting each note inside the stack.  The system will
tend to play each note with a different dynamic as it drifts out of
alignment.

Themodist systems don't have this drawback, and clearly the balance
between the gains of single-note themeing and the drawbacks of regu-
lation (and the dominance of Aeolian and other Themodist systems in
Europe) meant that Kastonome was not a commercial success.

Earlier postings contained a couple of mocking notes which should be
countered.  These simply extrapolated from known systems (which cannot
single-note theme) to the Kastonome, and therefore assumed from this
extrapolation that the Kastonome could not single-note theme either.
Very sloppy thinking!  Why the instant assumption that we are cleverer
than people in the past?

Consider the design details of the Kastonome.  It is a simple add-on
to an ordinary stack, with no external devices.  It is designed so the
restriction pouches only operate when the note is played, so avoiding
having 88 restriction pouches bleeding into the suction supply all the
time.  The accenting is performed by a tiny lightweight pouch, so is
very fast.  All this attention to detail suggests a carefully considered
and well-engineered design.  It may well be flawed in its over-reliance
on the pouch behaviour, but it seems by no means a bad idea, and indeed
in many ways a remarkably elegant one.

Julian Dyer

 [ Julian, could you please send us a sketch of the Kastonome pouch you
 [ describe, so that I can amend the web page at the MMD Tech site?
 [ Don't send attachments to <rolls> though; please email to me at
 [ <editor@foxtail.com>   Thanks.  --  Robbie